1. Field of the Invention
The present invention relates to a rubber composition comprising α,β-ethylenically unsaturated nitrile-conjugated diene copolymer rubber and ethylene-α-olefin copolymer rubber as main components, a vulcanizate of the rubber composition, and air intake hose composed of the vulcanizate.
2. Description of the Related Art
As a rubber material having oil resistance and ozone resistance at a time, chloroprene rubber is conventionally known. However, since the chloroprene rubber includes chlorine, it may bring an environment issue. Accordingly, as a substitution of the chloroprene rubber, a rubber composition of α,β-ethylenically unsaturated nitrile-conjugated diene copolymer rubber and ethylene-α-olefin copolymer rubber has been studied. However, they are not dissolved to each other when kneading only these two kinds of rubbers, so that vulcanizate to be obtained is excellent in ozone resistance but poor in mechanical strength and flexing fatigue resistance.
Accordingly, there has been a proposal of blending chlorinated polyethylene as a compatibilizing agent in the composition of α,β-ethylenically unsaturated nitrile-conjugated diene copolymer rubber and ethylene-α-olefin copolymer rubber (refer to the patent article 1).
However, the vulcanizate obtained by vulcanizing the composition described in the patent article 1 has excellent mechanical strength but has insufficient, flexing fatigue resistance. Also, since it includes chlorine, it may bring an environment issue.
Also, there has been disclosed (refer to the patent article 2) a rubber composition which can improve heat resisting durability and oil resistance, etc. by adding a specific graft polymer to acrylonitrile-butadiene copolymer rubber (a subordinate concept of α,β-ethylenically unsaturated nitrile-conjugated diene copolymer rubber) and ethylene-propylene copolymer rubber (a subordinate concept of ethylene-α-olefin copolymer rubber). The specific graft copolymer disclosed in the patent article 2 is obtained by performing graft copolymerization on a mixture of an aromatic vinyl compound and a polar vinyl compound (a leading concept of an α,β-ethylenically unsaturated nitrile monomer) with an ethylene-propylene-unconjugated diene copolymer.
Since the vulcanizate obtained by vulcanizing the composition described in the patent article 2 does not include chloride, it does not bring any environment issues but has a problem to be solved on flexing fatigue resistance.
Patent Article 1: the Japanese Unexamined Patent Publication No. 59 (1984)-199737
Patent Article 2: the Japanese Unexamined Patent Publication No. 54 (1979)-106554